Spirit Airlines' carry-on size limit is crucial for travelers to avoid additional fees. The maximum dimensions for a Spirit carry-on bag are 22 x 18 x 10 inches (56 x 46 x 25 cm), including handles and wheels. Passengers are allowed one free personal item, such as a small backpack or purse, that fits under the seat in front of them. For larger items, you must purchase a carry-on bag option during booking or at check-in. Adhering to these size limits ensures a smoother boarding process and helps avoid extra charges for oversized luggage. Always check current policies before your flight.